Air gun firing assembly

ABSTRACT

A quick action firing assembly for charging and suddenly releasing gas under pressure in a seismic energy generator for offshore subsurface exploration, for example, comprising a hollow, elongated valve having equal and opposite surfaces and means for charging the generator through the valve with high pressure gas and simultaneously applying equal forces in opposite directions to the valve whereby a minimum of force is required to open the valve.

United States Patent 1 [11] 3,800,832

Umphenour et al. 1 Apr. 2, 1974 AIR GUN FIRING ASSEMBLY 3,684,238 8/1972 Michcllone et al. 251/282 X [75] Inventors: Charles F. Umphenour; Reynaldo FOREIGN PATENTS OR APPLICATIONS Calderon both of Houston 1,208,592 9/1959 France l37/625.65 [73] Assignee: Texaco Inc., New York, NY.

Prima Examiner-Henr T. Klinksiek 22 F1 d: F 15.9 1972 Y 1 18 e Attorney, Agent, or Firm-T. H. Whaley; C. G. Ries [21] Appl. No.1 224,735

[57] ABSTRACT [52] US 137/625'65 181/5 A quick action firing assembly for charging and sud- 51 int. Cl. Fl6k 11/02 denly relwfsing g underbprersfsure I seismic Energy [58] Field of Search 181/5; 251/282; genera 9. S Ore ace exp or F ample, comprising a hollow, elongated valve having 137/625.65, 625.68

equal and opposlte surfaces and means for charging [561 321% fi3lIeLT $ilLZXJIS2J1?E;Z?Z UNITED STATES PATENTS, directions to the valve whereby a minimum of force is 3,379,273 4/1968 Chelminski l8l/,5 H required to open the valve, 3,473,557 10/1969 Loe l37/625.68 X 3,545,479 12/1970 Loe 137/625.68 X 7 Claims, 2 Drawing Figures PAIENIEBAPR 21914 DIRECTION OF TOW F/Gl AIR GUN FIIRING ASSEMBLY BACKGROUND OF THE INVENTION Broadly the present invention relates to seismic exploration and to an improved pneumatic marine seismic energy source for the introduction of seismic energy into water from a floating vessel for supplying compressed air and having a geophysical crew thereon for exploring earth layers and formations underlying bodies of water as oceans, seas, lakes, rivers, or the like. More particularly this invention pertains to a method and at least one mechanism for carrying out the method, one exemplary mechanism being a quick action firing assembly for efficiently charging a seismic energy generator chamber with a high pressure gas and likewise for quickly and efficiently releasing the high pressure gas from the chamber with an expenditure of a minimum of energy or force.

While the method and apparatus of the invention are applicable for many purposes as will be set forth further below, they are illustratively disclosed and described as applied to. underwater sound instrumentation such as oceanographic equipment and systems that are employed in seismic exploration of the worlds crust under and adjacent to bodies of water.

Since water is such a good sound conductor, it is unnecessary to generate sound waves right on or in the ocean floor; they can be produced in the water near the surface. The pressure waves travel down through the water to the ocean floor and are reflected as in the usual echo-sounding techniques. However, these waves also penetrate into the ocean floor and are reflected from the sub-strata. These acoustical waves also propagate horizontally through one or more geological strata and may be recorded at a distance from the source, thus providing useful refraction data on the stratum or strata involved.

Although explosives for marine seismic work can put large amounts of energy into the water and obtain great depth of penetration, they do have drawbacks; they are dangerous to handle and use, and in some areas such as congested harbors, they cannot be used at all. Also, each shot" is very expensive and can run into many thousands of dollars per survey. Explosives tend generally to concentrate substantial amounts of their energy output into higher frequency components which may not be desirable for many purposes; whereas, the sound impulse generation method and apparatus which the present invention is used on can be adjusted over a large amplitude range and adjusted in frequency so as to provide the desired spectrum distribution of sound frequencies for the purpose at hand.

The present invention is illustratively described as embodied in a device capable of emitting a large amount of acoustical energy into water in the form of a clear, repeatable pulse, the frequency and amplitude of which may be readily averred. These powerful sound impulses are well adapted for use in seismic exploration systems and also can be used to advantage for other purposes.

Seismic surveys which are conducted over water covered areas use various methods for generating seismic energy as by the detonating of conventional powder or dynamite, or gas mixtures, electrical discharge of sparks to ionize a portion of the water surrounding the electrode, or suddenly releasing a container of high pressure air underwater for generating a large seismic or pressure wave signal. These seismic signals are reflected from subsurface geological formations and structures and are received by seismometers and recorded.

In all methods utilized, it is customary to tow one or more detectors through the water in the vicinity of the sound source to detect the signals that are reflected from the various subsurface formations and structures. The detected signals are recorded on suitable equipment contained on the towing vessels, either in the form of analog or digital signals. Also, at times the signals are recorded as variable area signals to provide a profile of the surveyed area. The latter recording is similar to those contained with conventional depthsounding equipment.

All of the above seismic methods and devices have various disadvantages and thus none is completely suitable for use in all circumstances. The handling of an explosive material is, of course, dangerous as mentioned previously, wherein the explosions themselves tend to kill much marine life, an example of a seismic explosive device being disclosed in U.S. Pat. No. 2,877,859. Also, in the case of dynamite two separate vessels are requiredyone for handling the dynamite and the other for the recording equipment. This, of course, increases the cost of the survey.

Aside from the operational advantages over conventional dynamite surveys, the disclosed system affords better data acquisition through the effective and quicker acting pressure release valve having less back pressure to work against and requiring less power or voltage to actuate the actuating solenoid for firing a seismic acoustical energy generator or air gun.

The use of explosive gas mixture solves some of the problems that arise with dynamite, since explosive gas mixtures do not kill as much marine life, a further example being disclosed in U.S. Pat. No. 3,620,327. Normally, gas mixtures can be stored as separate, nonexplosive gases on the same vessel that contains the recording equipment. Thus, the need for an additional vessel or the possibility of killing marine life is reduced. While one disadvantage of gas type sound sources is the relatively short life of the flexible container or sleeve in which the explosive gas mixtures are detonated, conservation of the present environment is one of the principal problems.

In sound sources employing an electrical discharge, it has been customary to discharge a bank of capacitors charged to a high voltage through a single electrode or multiple parallel electrodes and a ground plate. When the capacitor bank is discharged into the water by the electrodes and ground plate the pressure bubble is produced at each electrode tip, for the ground plate serves as a return for the electrical energy. The pressure bubble produces the desired seismic impulse while the ground adds nothing to the magnitude of the outgoing acoustical wave. In fact, only 3-5 percent of the total electrical energy available in the capacitor bank is converted to useful acoustical energy in the water. Further, many spark electrodes in parallel may be used simultaneously as disclosed in U.S. Pat. No. 3,613,823.

DESCRIPTION OF PRIOR ART While compressed pneumatic guns as disclosed in U.S. Pat. Nos. 3,276,534 and 3,379,273 and assignees application Ser. No. 160,693, filed July 8, 1971 now US. Pat. No. 3,749,973, issued July 3 l I973, each has a passage through the plunger for the passage of air, none have the feature of equal and opposite areas normal to the longitudinal axis of the plunger for insuring a minimum required force to actuate the plunger to release the compressed air. The most pertinent disclosure, assignees above identified patent, illustrates an air gun in which a larger area and resultant force tending to maintain the plunger closed, in addition to the spring, must be overcome to open the valve, whereas the instant invention has only the force of the spring to overcome, resulting in a much faster operating seismic energy generator requiring less power or voltage to operate the solenoid for actuation of the valve.

OBJECTS OF THE INVENTION A primary object of this invention is to provide a method for charging a chamber with high pressure fluid and for quickly releasing the fluid with a minimum force.

Another primary object of this invention is to provide a device for carrying out the above method comprising a valve assembly for charging a chamber with high pressure fluid and simultaneously applying equal and opposite forces to the valve for requiring a minimum of valve opening forces.

Another object of this invention is to provide a hollow, spring loaded valve for supplying gas under pres sure to a chamber and a means for applying an equal force in both directions to the valve whereby a minimum force is required to open the valve.

A further object of this invention is to provide a valve having equal and opposite areas and means for applying a fluid pressure for developing equal and opposite forces on the valve so that a minimum force is required to open the valve.

Still another object of this invention is to provide an air gun firing assembly for a seismic energy source which is easy to operate, is of simple configuration, is economical to build and assemble, and is of greater efficiency for charging a seismic energy generator and for suddenly releasing the gas under high pressure for offshore subsurface exploration.

Other objects and various advantages of the disclosed firing assembly for an acoustical energy generator for offshore subsurface exploration will be apparent from the following detailed description, together with accompanying drawing, submitted for purposes of illustration only and not intended to define the scope of the invention, reference being had for that purpose to the subjoined claims.

BRIEF DESCRIPTION OF THE DRAWING The drawing diagrammatically illustrates by way of example, not by way of limitation, one form of the invention wherein like reference numerals have been employed to indicate similar parts in the several views in which:

FIG. 1 is a schematic sectional view of an embodiment of the new seismic energy generator having the new firing mechanism therein; and

FIG. 2 is a sectional view at 22 on FIG. 1.

DESCRIPTION OF THE PREFERRED METHOD OF THE INVENTION The invention disclosed herein, the scope of which being defined in the appended claims, is not limited in its application to the details of construction and arrangement of parts shown and described for carrying out the method, since the invention is capable of other embodiments for carrying out other methods and of being practiced or carried out in various other ways. Also, it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Further, many modifications and variations of the invention as hereinbefore set forth may occur to those skilled in the art. Therefore, all such modifications and variations which are within the spirit and scope of the invention herein are included and only such limitations should be imposed as are indicated in the appended claims.

This invention comprises both a method and a device for carrying out the method of charging a chamber with high pressure gas and for quickly releasing the gas with a minimum force.

This method comprises the steps of:

l. charging the chamber with high pressure fluid through a hollow closed valve, and

2. simultaneously applying equal forces in opposite directions to the valve so that only a minimum of force is required to open the valve for quick release of the fluid,

Step 2 comprises in greater detail:

1. applying fluid under pressure to equal areas of the valve in opposite directions simultaneously with charging of the chamber.

Modifying the second method step or adding a third method step comprises:

a. cutting off flow of high pressure fluid to the chamber simultaneously withapplying equal forces in opposite directions to the valve whereby only a minimum force is required to open the valve.

DESCRIPTION OF THE PREFERRED EMBODIMENT While various articles may be utilized for carrying out the above method of the invention, the preferred embodiment comprises a quick-action valve assembly for sudden release of gas under pressure from an inletexit port of a chamber of a seismic acoustical energy generator. Likewise, this valve assembly is utilized also for charging the high pressure chamber.

The disclosed firing assembly comprises, as shown in FIG. 1, a cylindrical housing 10 for containing the firing assembly and for attaching to a conventional acoustical pneumatic energy generator 11.

A typical seismic wave generator 11, FIG. 1, is lowered into the surrounding earth, marsh, or water, offshore or down in a conventional shot hole filled with water, for example. Accordingly, the generator is illustrated in an upright position sitting on its rear end in FIG. 1 for lowering in a shot hole, or with the top portion being the front end when being towed for offshore seismic exploration, for clarity of disclosure. While FIG. 1 illustrates the position of the seismic energy generator in vertical position for shot hole seismic surveying, the generator would be rotated clockwise to a horizontal position when being towed for offshore subsurface exploration.

The circular housing 10, FIG. 1, has an inlet 12 at the top connected to a suitable source of high pressure fluid, such as air, which is supplied to vertical main passage 13 for distribution to the air gun 11, and particularly to a high pressure air chamber (not shown) at the bottom of the air gun and to a firing mechanism at the top of the air gun.

The air gun has a smaller chamber 14 having an inletexit port or opening 15, outlet passages 16 and 17, and exhaust port 18 from which the expanding air rushes out to the surrounding water. The chamber inlet exit port is shown closed by the new hollow plunger valve 19.

The hollow plunger valve 19 comprises two parts, a larger hollow body part 19a positioned at the top for enclosing a spring 20 and a smaller hollow part or plunger stern 19b screwed into the plunger body. The body 19a of the plunger is slidable over a stud 21 screwed in plunger valve guide 22 in housing 10. Thus, when the plunger'va'lv'e is moved upwardly and opened, the high pressure air may escape from chamber 14 out through exhaust passages 16 and 17 to exit from the exhaust port 18 to escape out into the surrounding water. As shown in FIG. 2, three sets of exhaust passages are preferable. The hollow plunger is shown closing the opening and is held in closed position with the spring 20.

High pressure air from the supply passage 13 likewise travels transversely through a firing assembly first passage 23 to an annular second passage 24 around the portion 19b of the plunger. While a sloppy fit is shown between the cylindrical portion 19b and the walls of the passage 24, FIG. 1, leakage, of the air downwardly and outwardly to outlet passages 16 and 17 is prevented by sealing O-ring 25 in the housing. From there the air travels through a larger portion of the annular second passage 24 surrounding the plunger larger portion 190. Both upper and lower flat ends 26 and 27, respectively, of the larger portion 190 of the plunger and the flat ends 28 and 29, respectively, of the smaller portion 1917 are formed to the same identical areas, respectively, and are normal to the longitudinal axis of the plunger. Thus, as the air under pressure passes through the annular passage 24, around the smaller and larger portions of the plunger, and since these air passages are formed with the sloppy fit, as illustrated in FIG. 1, resulting in negligible air resistance, the air correspondingly arrives at both ends of each of the two valve portions, 19a and 19b practically simultaneously and accordingly the forces are neutralized for actuating the plunger in either direction. Third passages 30 extend from this second cylindrical passage 24 to the interior of the hollow plunger valve 19. From the hollow portion of the plunger the air passes to the chamber for charging it with high pressure air. Respective O-rings 31 and 32 for sealing are provided between the two portions 19a and 19b of the plunger valve and in the air gun around the inlet-exit opening 15 of the chamber, respectively.

A solenoid 34 is mounted in the housing around at least a portion of the plunger and has electrical wires 35 passing to electrical plug 36 for plugging into a suitable energy source for energizing the solenoid. Further, an O-ring 33 is mounted around the end of the stud that protrudes into the plunger. Upon actuation of the solenoid 34, the plunger 19a is moved upwardly in plunger guide 22, the spring 20 is compressed, and the plunger third passages 30 are sealed closed by the stud O-ring 33. When these latter passages are closed, no fluid is allowed to flow internally of the plunger nor to pass out of the plunger to charge the attached air gun. With equal pressure on equal and opposite plunger ends, the

solenoid has to overcome only the force of the spring to actuate plunger valve 19 to open chamber inlet-exit port 15, the friction and drag of the air passing through the passages being negligible. Also with a small portion of the area of the flat end 29 being covered with O-ring 32 and accordingly resulting in a small force differential caused by uncovered equal area flat end 28, the opening force generated by the solenoid is so great that this small force differential opposing the opening force is effectively negligible.

FIG. 2, a sectional view of 2-2 on FIG. 1, illustrates the requirement of three sets of outlet passages and exhaust ports, 17 and 18, respectively, while only one transverse high pressure fluid passage 23 is required.

Thus in operation, as high pressure fluid passes through the main passage 13 to charge the high pressure chamber of the air gun, this high pressure fluid or air also simultaneously passes through the first transverse passage 23 and from there it flows to the second passage 24, and continues on through the third passages 30 of the plunger into the internal or hollow portion of the plunger valve. From here the high pressure air flows the length of the plunger valve through chamber inlet-exit port 15 to further charge the chamber.

It may be noted that the force of the spring is the only means required and utilized for holding and maintaining the plunger valve against the opening and for sealing the opening. With the plunger in this position, equal pressure is applied to both opposite ends of both plunger valve parts and accordingly equal and opposite forces are applied thereto, which counteracting forces maintain the plunger at either of its positions. To fire the air gun, the solenoid is energized which then jerks the plunger upwardly to the left in FIG. 1 and away from the inlet-exit port 15. The action of the solenoid is only opposed by the spring in that immediately upon upward actuation of the plunger the third passages are closed by O-ring 33, thereby cancelling out or stopping the flow of high pressure fluid through the center of the plunger and the air pressure maintains equal and opposite forces on the ends of the plunger valve. Accordingly, upon actuation of the plunger upwardly, the high pressure fluid from the chamber is allowed to rush out of the opening 15 through the exhaust passages 16 and 17 and out the exhaust port 18 to the surrounding water for triggering the attached air gun for generating the acoustical seismic sound wave for subsurface exploration. When the plunger is at either of its end positions and because the forces are equalized due to being applied to both ends of the plunger, a minimum of force is required to open the plunger valve. Thus a high pressure air supply and quick-action valve assembly is disclosed for charging a chamber having an inlet-exit port and for suddenly exhausting the high pressure air therefrom.

Accordingly, it will be seen that the present firing assembly for the seismic energy source for off-shore subsurface exploration operates in a manner which meets each of the objects set forth hereinbefore.

While only one method and one embodiment for carrying out the method of the invention have been disclosed, it will be evident that various other methods and modifications are possible in the arrangement and construction of the disclosed firing assembly for a seismic energy generator for offshore subsurface explora tion without departing from the scope of the invention, and it is accordingly desired to comprehend within the purview of this invention such modifications as may be considered to fall within the scope of the appended claims.

We claim:

1. A quick action firing assembly for sudden release of gas under pressure from an exit port of a compressed gas seismic energy generator comprising,

a. spring loaded valve means having longitudinal movement in the seismic energy generator and being spring urged in one direction for closing said exit port, and

b. fluid pressure passage means for applying substantially an equal fluid force to two pairs of flat surfaces on said valve means in both longitudinal directions to said valve means whereby substantially only the force to overcome the spring is required to open said spring loaded valve means.

2. A quick action firing assembly as recited in claim 1 wherein,

a. said fluid pressure passage means comprises a first fluid passage through the longitudinal length of said spring biased valve means for pressurizing said seismic energy generator.

3. A quick action firing assembly as recited in claim 2 wherein,

a. said spring biased valve means has equal and opposite areas normal to its longitudinal axis, and

b. said fluid pressure passage means comprises a second passage to said equal and opposite areas on said spring biased valve means for applying substantially equal and opposite fluid forces longitudinally to said spring biased valve means.

4. A quick action firing assembly as recited in claim 3 wherein,

a. said fluid pressure passage means comprises a third passage transversely through said spring biased valve means connected to said second passage for pressurizing said seismic energy generator,

b. said seismic energy generator has stud means. and

c. said stud means is responsive to said spring biased valve means when it is opened for closing said third passage for stopping the flow of pressurized fluid to said seismic energy generator.

5. A quick action firing assembly as recited in claim 1 wherein,

a. said fluid pressure passage means comprises a second fluid passage to equal and opposite areas of said two pairs of flat surfaces on said spring biased valve means for applying substantially equal and opposite longitudinal fluid forces to said spring biased valve means.

6. A quick action firing assembly as recited in claim 1 wherein,

a. said seismic energy generator has actuating means,

and

b. said spring biased valve means is responsive to said actuating means for opening said seismic energy generator exit port for sudden release of pressurized gas from said seismic energy generator.

7. A quick action firing assembly as recited in claim 6 wherein,

a. said actuating means is a solenoid mounted on said seismic energy generator around at least a portion of said spring biased valve means for quickly moving the latter against the action of its spring for quick opening of said seismic energy generator exit port. 

1. A quick action firing assembly for sudden release of gas under pressure from an exit port of a compressed gas seismic energy generator comprising, a. spring loaded valve means having longitudinal movement in the seismic energy generator and being spring urged in one direction for closing said exit port, and b. fluid pressure passage means for applying substantially an equal fluid force to two pairs of flat surfaces on said valve means in both longitudinal directions to said valve means whereby substantially only the force to overcome the spring is required to open said spring loaded valve means.
 2. A quick action firing assembly as recited in claim 1 wherein, a. said fluid pressure passage means comprises a first fluid passage through the longitudinal length of said spring biased valve means for pressurizing said seismic energy generator.
 3. A quick action firing assembly as recited in claim 2 wherein, a. said spring biased valve means has equal and opposite areas normal to its longitudinal axis, and b. said fluid pressure passage means comprises a second passage to said equal and opposite areas on said spring biased valve means for applying substantially equal and opposite fluid forces longitudinally to said spring biased valve means.
 4. A quick action firing assembly as recited in claim 3 wherein, a. said fluid pressure passage means comprises a third passage transversely through said spring biased valve means connected to said second passage for pressurizing said seismic energy generator, b. said seismic energy generator has stud means, and c. said stud means is responsive to said spring biased valve means when it is opened for closing said third passage for stopping the flow of pressurized fluid to said seismic energy generator.
 5. A quick action firing assembly as recited in claim 1 wherein, a. said fluid pressure passage means comprises a second fluid passage to equal and opposite areas of said two pairs of flat surfaces on said spring biased valve means for applying substantially equal and opposite longitudinal fluid forces to said spring biased valve means.
 6. A quick action firing assembly as recited in claim 1 wherein, a. said seismic energy generator has actuating means, and b. said spring biased valve means is responsive to said actuating means for opening said seismic energy generator exit port for sudden release of pressurized gas from said seismic energy generator.
 7. A quick Action firing assembly as recited in claim 6 wherein, a. said actuating means is a solenoid mounted on said seismic energy generator around at least a portion of said spring biased valve means for quickly moving the latter against the action of its spring for quick opening of said seismic energy generator exit port. 